Color filter for light bulbs and sign construction embodying same



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United States Patent 3,312,814 COLOR FILTER FOR LIGHT BULBS AND SIGN I CONSTRUCTION EMBODYING SAME Oscar W. Reading, Kansas City, Mo., assignor of fortynine percent to Ben Berg, Kansas City, Mo. Filed July 15, 1964, Ser. No. 382,826 1 Claim. (Cl. 240--46.57)

This invention relates to new and useful improvements in the electric sign art, and has as its principal object the provision of a color filter whereby the apparent color of electric light bulbs as used in electric display signs may be altered at will without necessity of purchasing light bulbs originally manufactured with the desired color permanently applied thereto, said filter being easily removable and transferable from one bulb to another, so as to be transferred from a burned out bulb to a new bulb, or so as to be moved from one bulb to another in a particular sign to vary the color pattern of the sign without necessity of changing or handling the bulbs themselves. The filter is ordinarily used with clear bulbs producing a white light, in order that any desired color may be produced by using the proper filter. Since clear bulbs can be purchased for a much lower price than comparable colored bulbs, and since one filter will last through the lifetimes of many bulbs, it will be apparent also that my filter produces a valuable economy in the operation and maintenance of electric signs.

Another object is the provision of a filter of the character described which while changing the apparent color of the bulb as viewed from any normal angle, nevertheless provides for illumination of the panel in which the bulbs are mounted with a clear white light, whereby it is viewed in its own normal colors, to permit contrasts with the apparent bulb colors. In most electric signs using colored bulbs, the panel darkens or fades into insignificance, and is hardly noticeable at all, unless it is of the same color as the bulbs, since a panel of a given color will tend to reflect only light of its own color.

Other objects are simplicity and economy of construction, efiiciency and dependability of operation, and adaptability to produce a wide variety of decorative and pleasing eifects.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. 1 is a fragmentary sectional view through the panel of an electric sign including a series of electric light bulbs, each of said bulbs having a color filter embodying the present invention applied operatively thereto, r

FIG. 2 is a fragmentary sectional view taken on line IIII of FIG. 1, with the bulb left in elevation,

FIG. 3 is a sectional view taken on line III-III of FIG. 2, with the bulb left in elevation, and

FIG. 4 is an open-end view of the filter removed from the bulb.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies to the panel of an electric sign of the type including a series of light bulbs 4 arranged on the outer surface of the panel. Said bulbs are usually arranged in patterns, or in solid banks forming patterns, and large signs often include hundreds or even thousands of bulbs. The bulbs are ordinarily spaced on about 4-inch centers, and are commonly of or 11 watt power with the size and shape shown in the drawing, each bulb being generally spherically bulbous in form at its outer end and conically tapered to a screw base 6, the bulbs being mounted by threading base 6 into a socket member 8 secured in panel 2 by bolts 10, said socket member being provided, behind the panel, with terminal posts 12 for the connection of 3,312,814 Patented Apr. 4, 1967 wires furnishing. electric power to the bulb. The filament and other internal construction of the bulb is standard and is not illustrated, though it will be understood that the filament is generally centered in the bulbous end portion of the bulb. To my knowledge, it has heretofore been necessary to purchase colored light bulbs whenever it is desired to use color as a feature of the sign, the color being permanently applied by the manufacturer in the form of a paint-like coating applied to either the inner or outer surface of the bulb. These coatings are available only in a limited number of colors, and do not transmit true, pleasing colors. Also, such colored bulbs are much more expensive than clear bulbs, so that the maintenance cost of replacing burned out bulbs in a large sign is multiplied.

According to the present invention, clear bulbs may be used, and any desired color provided for each bulb, by a color filter indicated generally by the numeral 14 and consisting of a cup-shaped body member formed of a transparent or translucent material, preferably a molded plastic, of the desired color. It is of a size and shape adapted to fit over the bulbous end of the glass envelope of the bulb in coaxial relationship thereto, having a generally spherical closed-end portion 16 and a cylindrical skirt 18 at the open end thereof. The internal dimension of the filter is somewhat larger than the bulb, in order to provide an air space therebetween for the circulation of air to prevent overheating of the bulb. The bulbs ordinarily used in electric sign work are of sufficiently low wattage that they do not become particularly hot when fully exposed to the atmosphere, but tightly enclosing them .with the filters might so insulate them against the escape of heat that overheating could occur, or softening of the plastic material of the filters themselves might occur, were it not for the spacing described.

The filter is held in properly spaced relation to the bulb surface by a plurality of ribs 20 formed integrally on the inner surface of the filter and directly engaging the surface of the bulb, said ribs each extending from a point adjacent the center of the filter to a point adjacent the periphery thereof, in a plane containing the axis of the cup, and extending past the plane of the maximum bulb diameter so as to overhang and conform to the tapered portion. of the bulb, as at 22, whereby to hold the filter firmly in position on the bulb. However, the amount of the overhang is sufiiciently slight, and the plastic is sufficiently elastic, that the filter may easily be applied or removed by direct manual pressure thereon in a direction parallel to the bulb axis. This elasticity of the plastic also permits the withdrawal of the internal mold during the manufacture thereof. The ribs are inwardly tapered, as best shown in FIG. 3, whereby to provide minimum contact area with the bulb. The ribs are terminated short of the center of the filter whereby to provide an air passage 24 (see FIGS. 2 and 4) from one side of the filter to the other. The ribs thus do not form closed pockets between the bulb and filter which could inhibit free circulation of air.

The skirt portion 18 of the filter may of course be of any desired length, and could be of such length as to reach substantially all the way to panel 2 and thus substantially completely enclose the bulb, although in that case the ribs should be of no greater length than shown, in order that the filter could still be applied to and removed from the bulb as described. However, making the total depth of the filter cup considerably less than the axial length of the bulb, as illustrated, permits an unusual display effect in the sign construction shown, in that it leaves a portion of the bulb exposed so that if a clear bulb is used, white light from the exposed portion of the bulb will illuminate the face of panel 2, as indicontrast to the filter color.

cated by the light rays 26 in FIG. 1, so that the panel will appear in its own normal color even though it may As previously explained, light from a colored bulb will not effectively illuminate a panel of a contrasting color, since by definition a colored panel is one which will effectively reflect only light of its own color. This creates many novel possibilities of display, for example in contrasting the panel and bulb colors, using colored designs on the panel, and the like.

It will be apparent that my color filter provides several advantages. It provides a colored-bulb effect while permitting the use of clear bulbs which are much less expensive than colored bulbs. The filters may be shifted from bulb to bulb to permit changing of color patterns on designs without changing bulbs, and may be transferred to new bulbs as old ones burn out, one filter being capable of outlasting the operative lives of many bulbs. The filters will not cause overheating of the bulbs to shorten the lives thereof. The filters permit the use of plastics or the like having a much greater range and effectiveness of color and decorative possibilities than can be provided in permanently colored bulbs. For example, since the filter is much thicker than the glass of the bulb and is colored throughout its thickness, they provide transparent colors of much greater depth and richness than is possible with thin bulb coatings. This thickness also permits decorative material, such for example as shiny reflective particles, to be molded therein to provide a glittering or sparkling appearance. The filters also could be opaque or nearly opaque to provide only indirect lighting of the panel, or partially opaque and partially transparent or translucent in any desired color to provide patterned lighting effects.

While I have shown and described a specific embodiment of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention as defined by the scope of the appended claim.

What I claim is:

A color filter for a light bulb having a transverse maximum diameter at a point intermediate the free and base ends thereof, said color filter comprising:

(a) a cup-shaped body member of translucent colored elastic material adapted to be applied over the free end of said bulb to enclose the free end portion thereof, the transverse internal dimensions of said body member being larger than the exterior dimensions of the portion of the bulb enclosed thereby, whereby to provide a space therebetween for the circulation of air, and the internal depth of said body member being sufficient to enclose the maxi mum diameter of said bulb, and

(b) spacer members aflixed to the inner surface of said body member and operable to engage said bulb to maintain said body member in centered relationship thereto, said spacer members traversing the maximum diameter of said bulb, the portions of said spacer members adjacent the open end of said body member defining a diameter slightly less than the maximum diameter of said bulb, whereby they may be defiected outwardly by elastic yieldability of said body member to pass over the maximum diameter of said bulb, and thereafter maintain said body member yieldably in assembly with said bulb.

References Cited by the Examiner UNITED STATES PATENTS 1,042,979 10/1912 Seessle 240-46.S5 X 1,461,924 7/1923 Luyties 240-4659 X 1,511,412 10/1924 Lyon 240-4655 1,778,061 10/1930 Butler 240-46.55 X 1,871,552 8/1932 Padesky 240-816 2,734,129 2/1956 Kahla 240-46.59

NORTON ANSHER, Prinmry Examiner. C. R. RHODES, Assistant Examiner. 

